In certain known passenger aircraft, the entry and service doors open inward and upward into the overhead area above the ceiling panels. In order to permit passage of each door, the ceiling lining panels in the vicinity of the door must retract. Known retraction mechanisms include a hinge at the juncture of the ceiling panels and the door liner panels. Since important equipment is stored inside the door behind the door liner panels and since much of the door operating mechanism is located behind such panels, there must be access to the inside of the door for maintenance of the equipment and the door. Therefore, the hinge between the door and ceiling must be readily detachable in order to provide such access.
A known hinge structure that has been used at the juncture of the ceiling and door is a structure in which four discrete hinges are attached to two release bars in order to allow their quick release. Each of these four hinges includes a spring-loaded hinge pin; i.e., a hinge pin having its own separate spring bearing axially against it to urge it into an engaged position. The use of a hinge structure having discrete hinges and spring-loaded pins has presented a number of problems. Because of the difficulty in maintaining accurate alignment of the separate hinge segments along the relatively long hinge axis, the pins have a tendency to bind. This results in distortion of the structure and breakage of the release knobs. In addition, of necessity each spring in the hinge structure is relatively small and must be substantially fully compressed to disengage the hinge structure. Consequently, the life of the springs is relatively short, and thus, the maintenance costs relating to the hinge structure are relatively high.
The patent literature includes a number of examples of hinge structures that include a spring or springs. Such structures are disclosed in U.S. Pat. Nos.: 1,194,628, granted Aug. 15, 1916, to J. Hist; 1,332,591, granted Mar. 2, 1920, to K. B. Arthur; 1,904,110, granted Apr. 18, 1933, to P. Willmann; 2,534,998, granted Dec. 19, 1950, to W. Steinbach; 2,987,782, granted June 13, 1961, to W. J. Kurowski; 3,032,777, granted May 8, 1962, to S. L. Young; 3,210,800, granted Oct. 12, 1965, to R. W. Navarro et al; 3,510,986, granted May 12, 1970, to I. L. Berkowitz; 3,671,998, granted June 27, 1972, to J. A. Ruiz; 3,673,636, granted July 4, 1972, to J. A. Ruiz; 3,908,227, granted Sept. 30, 1975, to J. F. Cain; 4,178,657, granted Dec. 18, 1979, to L. V. Way, Jr.; and 4,307,486, granted Dec. 29, 1981, to S. Matsumoto.
Each of the above patents, except Way, Jr. and Matsumoto, discloses a hinge mechanism in which a spring or springs coaxial with the hinge pins urges the pins into an enraged position. The spring in the Matsumoto mechanism connects two hinge leaves and itself acts as a hinge pin. In the hinge mechanism disclosed by Way, Jr., two hinge pins are retractable into a center hinge knuckle. An actuating mechanism including two levers pivotably connected to each other is provided. One end of each lever is attached to one of the pins. To release the hinge mechanism, one of the levers is moved to impart a combination of pivotal and sliding motion to each of the two levers to in turn slide the hinge pins toward each other into the center hinge knuckle. A torsion spring oriented perpendicularly to the hinge axis is provided at the pivotal connection between the two levers to bias the levers into either one of their two extreme positions.
The known structures and the patents discussed above and the prior art discussed and/or cited in the patents should be carefully considered for the purpose of putting the present invention into proper perspective relative to the prior art.